libpsi: Add explicit header files

The libpsi source code is missing cutils and stdio header files.
Add cutils and stdio header files, and add libcutils_headers to
the header library in Android.bp.

Bug: 169346507
Change-Id: I2d613d5724d3c5f52dd52dcae7024439f2e8d5bb
Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>

libpsi/Android.bp

@@ -11,6 +11,7 @@ cc_library {
     ],
     header_libs: [
         "libpsi_headers",
+        "libcutils_headers",
     ],
     export_header_lib_headers: [
         "libpsi_headers",

libpsi/psi.cpp

@@ -24,6 +24,8 @@
 #include <unistd.h>
 
 #include <log/log.h>
+#include <cutils/fs.h>
+#include <stdio.h>
 #include "psi/psi.h"
 
 #define PSI_MON_FILE_MEMORY "/proc/pressure/memory"